Photochromism of an azobenzene in a nanoporous silica film

The incorporation of a cationic azobenzene derivative, p-(ω-dimethylethanolammonioethoxy)-azobenzene bromide, into nanoporous silica films and the photochemical reactions of the adsorbed dye were investigated. The nanoporous silica films were prepared from tetramethoxysilane and octadecyltrimethylammonium chloride by the rapid solvent evaporation method which we have reported previously. The adsorption of the cationic azo dye was conducted by casting an ethanol solution of the dye onto the nanoporous silica films. Upon UV light irradiation, frans-azobenzene isomerized photochemically to the cis-form and photochemically formed cis-form turned back to the trans-form upon visible light irradiation. The nanoporous silica films were proved to be an excellent reaction media to immobilize organic photocromic species.